Sorry I can't be of help on the earlier years. I used this as a guide for 79-80 trucks:
The Definitive 79-80 Desmog Guide - https://forum.ih8mud.com/threads/the-definitive-79-80-desmog-guide.812197/
This thread may have some pics that are helpful
My Desmog Keeping HAC Lots of Pics -...
I think you answered your own question.The only people who seem to keep the emissions are those living in a smog state(mainly CA owners) and the nut and bolt concours restoration folks.
No harm in removing properly, cleans the engine bay up alot.Definetly save the parts as you mention.